In the existing radiation inspection system, the radiation beam emitted by a radiation source located on one side of a system after passing through a collimator may form a “sector” beam surface. The detector module is located on the other side of the system, and an inspected object is between the radiation beam and the detector module. As shown in FIG. 1, the radiation beam a5 emitted by the radiation source a1 after penetrating the inspected object a2, is emitted towards a plurality of detector modules a4 on a detector module mount a3. The existing detector module usually consists of certain amount of higher energy and lower energy detector arrays. All the detector modules are oriented towards a radiation source point.
For a dual energy detector, as shown in FIG. 2, the lower energy detector array a41 and the higher energy detector array a45 are generally provided in a front-and-rear positional relation. Wherein, the lower energy detector array a41 is located on one side proximate to the radiation source a1, while the higher energy detector array a45 is disposed on one side distant from the radiation source a1. The radiation beam a5 penetrates the lower energy detector array a41 before reaching the higher energy detector array a45. The lower energy detector array a41 relatively absorbs more energy of low energy rays, and the higher energy detector array a45 relatively absorbs more high energy rays. Finally, such two signals are analyzed to obtain information of an effective atomic number of an inspected substance. A photodiode a42 and a printed circuit board a43 are provided on a rear side of the lower energy detector array a41, and a photodiode a46 and a printed circuit board a47 are provided on a rear side of the higher energy detector array a45. In use, the lower energy detector array a41, in addition to acquiring the low energy signal, also assumes the filtering function of the higher energy detector array a45 by means of a filter a44.
The structure of this existing dual-energy detector is very universal at present, and in the specific implementation, there are the following problems:
1. Each detector module has a fixed orientation at the installation location. The orientation is directed to a target point of the radiation source. The design is relatively complicated and the installation and debugging are very difficult. Moreover, if the overall geometry varies (such as a position of the radiation source), the entire detector module mount needs to be re-designed. Further, in order to stably install the detector module, the detector module mount needs to be made to be relatively thick, so that it is quite inconvenient in terms of installation and use.
2. The detector modules are so unsmooth therebetween that, the detector at an edge of an edge module is susceptible to scattering interference.
3. The sensitive medium of the lower energy detector array is limited in an optional range, and thus is not a desirable filtering material. For the lower energy detector array, the area of the photodiodes on a rear side thereof may generally be less than the area of the lower energy detector array, but does not match the sensitive area of the lower energy detector.
4. In actual use, the width of the radiation beam at the detector module which is difficult to be constrained to the width of a sensitive area of the detector, may generally substantially exceed the width of a single detector array, resulting in an additional radiation protection pressure.